package org.jgrasstools.gears.io.disktree.jtstmp;

import java.io.Serializable;

import com.vividsolutions.jts.geom.Coordinate;
import com.vividsolutions.jts.geom.Envelope;

/**
 * A Key is a unique identifier for a node in a quadtree.
 * It contains a lower-left point and a level number. The level number
 * is the power of two for the size of the node envelope
 *
 * @version 1.7
 */
public class Key implements Serializable {

    private static final long serialVersionUID = -6333591104807918622L;

    public static int computeQuadLevel( Envelope env ) {
        double dx = env.getWidth();
        double dy = env.getHeight();
        double dMax = dx > dy ? dx : dy;
        int level = DoubleBits.exponent(dMax) + 1;
        return level;
    }

    // the fields which make up the key
    private Coordinate pt = new Coordinate();
    private int level = 0;
    // auxiliary data which is derived from the key for use in computation
    private Envelope env = null;

    public Key( Envelope itemEnv ) {
        computeKey(itemEnv);
    }

    public Coordinate getPoint() {
        return pt;
    }
    public int getLevel() {
        return level;
    }
    public Envelope getEnvelope() {
        return env;
    }

    public Coordinate getCentre() {
        return new Coordinate((env.getMinX() + env.getMaxX()) / 2, (env.getMinY() + env.getMaxY()) / 2);
    }
    /**
     * return a square envelope containing the argument envelope,
     * whose extent is a power of two and which is based at a power of 2
     */
    public void computeKey( Envelope itemEnv ) {
        level = computeQuadLevel(itemEnv);
        env = new Envelope();
        computeKey(level, itemEnv);
        // MD - would be nice to have a non-iterative form of this algorithm
        while( !env.contains(itemEnv) ) {
            level += 1;
            computeKey(level, itemEnv);
        }
    }

    private void computeKey( int level, Envelope itemEnv ) {
        double quadSize = DoubleBits.powerOf2(level);
        pt.x = Math.floor(itemEnv.getMinX() / quadSize) * quadSize;
        pt.y = Math.floor(itemEnv.getMinY() / quadSize) * quadSize;
        env.init(pt.x, pt.x + quadSize, pt.y, pt.y + quadSize);
    }
}
